REFLECTOR: Leaking sump float switch

[Jim Sower]

<... Is there any scenario with nonzero probability that would stop fuel flowing from both main tanks?...>

Assymmetric flow from the strakes to the sump is not uncommon.  If one 
strake is reluctant, the other can get quite a ways ahead of it, and go 
dry while the "reluctant" strake still has a substantial amount of 
fuel.  If transfer from this strake is insufficient to run the engine, 
you will draw down the sump tank. 
It's useful to know when that is happening. ... Jim S.


wurzel at alumni.caltech.edu wrote:

>Everyone, thanks for all the great advice and ideas (as always!)
>
>  
>
>>I still can't see any reason for a sump switch, unless it for the person
>>that has faulty fuel level sensors in the mains and also refuses to
>>calculate their fuel burn before and during the flight.
>>    
>>
>
>N570 has the visual sight gauges on both main tanks, and I
>love them.  I also have a fuel totalizer in the EDM-700,
>and I calculate my fuel burn before each flight.  During the
>flight, it gives me great pleasure and confidence to see
>that all three calculations are humming along in concert.
>I like the totalizer... but looking over my shoulder and
>seeing the fuel in the tubes is the final word.  (ie, if
>my fuel caps were leaking and I somehow didn't notice,
>my EDM-700 would be wrong, but my sight gauges wouldn't
>lie.)
>
>That said, I see your point about the sump low light being
>a bit gratuitous.  What additional failure scenarios does
>this really cover?  Is there any scenario with nonzero
>probability that would stop fuel flowing from both main tanks?
>If there were some kind of leak causing fuel to be dumped
>overboard, I would imagine you'd have some other indication
>long before the sump light turns on.
>
>Hmmmm, maybe I should just glass over it and pretend it
>never existed.  ;-)
>
>Seriously, my switch is here and now I just need to figure out
>a good way to store 30 gallons of fuel while I do the
>repair.  :-(
>
>                            -wurzel
>
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